Description: Type Ia supernovae are key tools for measuring distances on a cosmic scale. They are generally thought to be the thermonuclear explosion of an accreting white dwarf in a close binary system. The nature of the mass donor is still uncertain. In the single-degenerate model it is a main-sequence star or an evolved star, whereas in the double-degenerate model it is another white dwarf. We show that the velocity structure of absorbing material along the line of sight to 35 type Ia supernovae tends to be blueshifted. These structures are likely signatures of gas outflows from the supernova progenitor systems. Thus, many type Ia supernovae in nearby spiral galaxies may originate in single-degenerate systems.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sternberg, A -- Gal-Yam, A -- Simon, J D -- Leonard, D C -- Quimby, R M -- Phillips, M M -- Morrell, N -- Thompson, I B -- Ivans, I -- Marshall, J L -- Filippenko, A V -- Marcy, G W -- Bloom, J S -- Patat, F -- Foley, R J -- Yong, D -- Penprase, B E -- Beeler, D J -- Allende Prieto, C -- Stringfellow, G S -- New York, N.Y. -- Science. 2011 Aug 12;333(6044):856-9. doi: 10.1126/science.1203836.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Benoziyo Center for Astrophysics, Faculty of Physics, Weizmann Institute of Science, Rehovot 76100, Israel. assaf.sternberg@weizmann.ac.il〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21836010" target="_blank"〉PubMed〈/a〉

Description: We report the discovery of ASASSN-15lh (SN 2015L), which we interpret as the most luminous supernova yet found. At redshift z = 0.2326, ASASSN-15lh reached an absolute magnitude of Mu ,AB = -23.5 +/- 0.1 and bolometric luminosity Lbol = (2.2 +/- 0.2) x 10(45) ergs s(-1), which is more than twice as luminous as any previously known supernova. It has several major features characteristic of the hydrogen-poor super-luminous supernovae (SLSNe-I), whose energy sources and progenitors are currently poorly understood. In contrast to most previously known SLSNe-I that reside in star-forming dwarf galaxies, ASASSN-15lh appears to be hosted by a luminous galaxy (MK approximately -25.5) with little star formation. In the 4 months since first detection, ASASSN-15lh radiated (1.1 +/- 0.2) x 10(52) ergs, challenging the magnetar model for its engine.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dong, Subo -- Shappee, B J -- Prieto, J L -- Jha, S W -- Stanek, K Z -- Holoien, T W-S -- Kochanek, C S -- Thompson, T A -- Morrell, N -- Thompson, I B -- Basu, U -- Beacom, J F -- Bersier, D -- Brimacombe, J -- Brown, J S -- Bufano, F -- Chen, Ping -- Conseil, E -- Danilet, A B -- Falco, E -- Grupe, D -- Kiyota, S -- Masi, G -- Nicholls, B -- Olivares E, F -- Pignata, G -- Pojmanski, G -- Simonian, G V -- Szczygiel, D M -- Wozniak, P R -- New York, N.Y. -- Science. 2016 Jan 15;351(6270):257-60. doi: 10.1126/science.aac9613.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Road 5, Hai Dian District, Beijing 100871, China. dongsubo@pku.edu.cn. ; Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101, USA. ; Nucleo de Astronomia de la Facultad de Ingenieria, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile. Millennium Institute of Astrophysics, Santiago, Chile. ; Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854, USA. ; Department of Astronomy, The Ohio State University, 140 W. 18th Avenue, Columbus, OH 43210, USA. Center for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, 191 W. Woodruff Avenue, Columbus, OH 43210, USA. ; Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena, Chile. ; Department of Astronomy, The Ohio State University, 140 W. 18th Avenue, Columbus, OH 43210, USA. ; Department of Astronomy, The Ohio State University, 140 W. 18th Avenue, Columbus, OH 43210, USA. Center for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, 191 W. Woodruff Avenue, Columbus, OH 43210, USA. Department of Physics, The Ohio State University, 191 W. Woodruff Avenue, Columbus, OH 43210, USA. ; Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK. ; Coral Towers Observatory, Cairns, Queensland 4870, Australia. ; INAF-Osservatorio Astrofisico di Catania, Via S.Sofia 78, 95123, Catania, Italy. ; Department of Astronomy, Peking University, Yi He Yuan Road 5, Hai Dian District, 100871, P. R. China. ; Association Francaise des Observateurs d'Etoiles Variables (AFOEV), Observatoire de Strasbourg 11, rue de l'Universite, F-67000 Strasbourg, France. ; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA. ; Department of Earth and Space Science, Morehead State University, 235 Martindale Drive, Morehead, KY 40351, USA. ; Variable Star Observers League in Japan (VSOLJ), 7-1 Kitahatsutomi, Kamagaya, Chiba 273-0126, Japan. ; The Virtual Telescope Project, Via Madonna de Loco 47, 03023 Ceccano, Italy. ; Mt Vernon Observatory, 6 Mt Vernon pl, Nelson, New Zealand. ; Millennium Institute of Astrophysics, Santiago, Chile. Departamento Ciencias Fisicas, Universidad Andres Bello, Av. Republica 252, Santiago, Chile. ; Warsaw University Astronomical Observatory, Al. Ujazdowskie 4, 00-478 Warsaw, Poland. ; Los Alamos National Laboratory, Mail Stop B244, Los Alamos, NM 87545, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26816375" target="_blank"〉PubMed〈/a〉

Description: In the era of precision cosmology, it is essential to determine the Hubble constant to an accuracy of three per cent or better. At present, its uncertainty is dominated by the uncertainty in the distance to the Large Magellanic Cloud (LMC), which, being our second-closest galaxy, serves as the best anchor point for the cosmic distance scale. Observations of eclipsing binaries offer a unique opportunity to measure stellar parameters and distances precisely and accurately. The eclipsing-binary method was previously applied to the LMC, but the accuracy of the distance results was lessened by the need to model the bright, early-type systems used in those studies. Here we report determinations of the distances to eight long-period, late-type eclipsing systems in the LMC, composed of cool, giant stars. For these systems, we can accurately measure both the linear and the angular sizes of their components and avoid the most important problems related to the hot, early-type systems. The LMC distance that we derive from these systems (49.97 +/- 0.19 (statistical) +/- 1.11 (systematic) kiloparsecs) is accurate to 2.2 per cent and provides a firm base for a 3-per-cent determination of the Hubble constant, with prospects for improvement to 2 per cent in the future.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pietrzynski, G -- Graczyk, D -- Gieren, W -- Thompson, I B -- Pilecki, B -- Udalski, A -- Soszynski, I -- Kozlowski, S -- Konorski, P -- Suchomska, K -- Bono, G -- Moroni, P G Prada -- Villanova, S -- Nardetto, N -- Bresolin, F -- Kudritzki, R P -- Storm, J -- Gallenne, A -- Smolec, R -- Minniti, D -- Kubiak, M -- Szymanski, M K -- Poleski, R -- Wyrzykowski, L -- Ulaczyk, K -- Pietrukowicz, P -- Gorski, M -- Karczmarek, P -- England -- Nature. 2013 Mar 7;495(7439):76-9. doi: 10.1038/nature11878.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Universidad de Concepcion, Departamento de Astronomia, Casilla 160-C, Concepcion, Chile. pietrzyn@astrouw.edu.pl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23467166" target="_blank"〉PubMed〈/a〉

Description: RR Lyrae pulsating stars have been extensively used as tracers of old stellar populations for the purpose of determining the ages of galaxies, and as tools to measure distances to nearby galaxies. There was accordingly considerable interest when the RR Lyrae star OGLE-BLG-RRLYR-02792 (referred to here as RRLYR-02792) was found to be a member of an eclipsing binary system, because the mass of the pulsator (hitherto constrained only by models) could be unambiguously determined. Here we report that RRLYR-02792 has a mass of 0.26 solar masses M[symbol see text] and therefore cannot be a classical RR Lyrae star. Using models, we find that its properties are best explained by the evolution of a close binary system that started with M[symbol see text] and 0.8M[symbol see text]stars orbiting each other with an initial period of 2.9 days. Mass exchange over 5.4 billion years produced the observed system, which is now in a very short-lived phase where the physical properties of the pulsator happen to place it in the same instability strip of the Hertzsprung-Russell diagram as that occupied by RR Lyrae stars. We estimate that only 0.2 per cent of RR Lyrae stars may be contaminated by systems similar to this one, which implies that distances measured with RR Lyrae stars should not be significantly affected by these binary interlopers.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pietrzynski, G -- Thompson, I B -- Gieren, W -- Graczyk, D -- Stepien, K -- Bono, G -- Moroni, P G Prada -- Pilecki, B -- Udalski, A -- Soszynski, I -- Preston, G W -- Nardetto, N -- McWilliam, A -- Roederer, I U -- Gorski, M -- Konorski, P -- Storm, J -- England -- Nature. 2012 Apr 4;484(7392):75-7. doi: 10.1038/nature10966.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Departamento de Astronomia, Universidad de Concepcion, Casilla 160-C, Concepcion, Chile. pietrzyn@astrouw.edu.pl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22481359" target="_blank"〉PubMed〈/a〉

Description: We have analyzed the double-lined eclipsing binary system ASAS J180057-2333.8 from the All Sky Automated Survey (ASAS) catalogue. We measure absolute physical and orbital parameters for this system based on archival V -band and I -band ASAS photometry, as well as on high-resolution spectroscopic data obtained with ESO 3.6 m/HARPS and CORALIE spectrographs. The physical and orbital parameters of the system were derived with an accuracy of about 0.5–3 per cent. The system is a very rare configuration of two bright well-detached giants of spectral types K1 and K4 and luminosity class II. The radii of the stars are R 1 = 52.12 ± 1.38 and R 2 = 67.63 ± 1.40 R and their masses are M 1 = 4.914 ± 0.021 and M 2 = 4.875 ± 0.021 M . The exquisite accuracy of 0.5 per cent obtained for the masses of the components is one of the best mass determinations for giants. We derived a precise distance to the system of 2.14 ± 0.06 kpc (stat.) ± 0.05 (syst.) which places the star in the Sagittarius–Carina arm. The Galactic rotational velocity of the star is s = 258 ± 26 km s –1 assuming 0 = 238 km s –1 . A comparison with parsec isochrones places the system at the early phase of core helium burning with an age of slightly larger than 100 million years. The effect of overshooting on stellar evolutionary tracks was explored using the mesa star code.

Description: A novel method of analysis of double-lined eclipsing binaries containing a radially pulsating star is presented. The combined pulsating–eclipsing light curve is built up from a purely eclipsing light-curve grid created using an existing modelling tool. For every pulsation phase, the instantaneous radius and surface brightness are taken into account, being calculated from the disentangled radial velocity curve of the pulsating star and from its out-of-eclipse pulsational light curve and the light ratio of the components, respectively. The best model is found using the Markov chain Monte Carlo method. The method is applied to the eclipsing binary Cepheid OGLE-LMC-CEP-0227 ( P puls  = 3.80 d, P orb  = 309 d). We analyse a set of new spectroscopic and photometric observations for this binary, simultaneously fitting OGLE V -band, I -band and Spitzer 3.6 μm photometry. We derive a set of fundamental parameters of the system significantly improving the precision comparing to the previous results obtained by our group. The Cepheid mass and radius are M 1  = 4.165 ± 0.032 M and R 1  = 34.92 ± 0.34 R , respectively. For the first time a direct, geometrical and distance-independent determination of the Cepheid projection factor is presented. The value p = 1.21 ± 0.03(stat.) ± 0.04(syst.) is consistent with theoretical expectations for a short-period Cepheid and interferometric measurements for Cep. We also find a very high value of the optical limb darkening coefficients for the Cepheid component, in strong disagreement with theoretical predictions for static atmospheres at a given surface temperature and gravity.

Description: Exoplanets of a few Earth masses can be now detected around nearby low-mass stars using Doppler spectroscopy. In this Letter, we investigate the radial velocity variations of Kapteyn's star, which is both a sub-dwarf M-star and the nearest halo object to the Sun. The observations comprise archival and new HARPS (High Accuracy Radial velocity Planet Searcher), High Resolution Echelle Spectrometer (HIRES) and Planet Finder Spectrograph (PFS) Doppler measurements. Two Doppler signals are detected at periods of 48 and 120 d using likelihood periodograms and a Bayesian analysis of the data. Using the same techniques, the activity indices and archival All Sky Automated Survey (ASAS-3) photometry show evidence for low-level activity periodicities of the order of several hundred days. However, there are no significant correlations with the radial velocity variations on the same time-scales. The inclusion of planetary Keplerian signals in the model results in levels of correlated and excess white noise that are remarkably low compared to younger G, K and M dwarfs. We conclude that Kapteyn's star is most probably orbited by two super-Earth mass planets, one of which is orbiting in its circumstellar habitable zone, becoming the oldest potentially habitable planet known to date. The presence and long-term survival of a planetary system seem a remarkable feat given the peculiar origin and kinematic history of Kapteyn's star. The detection of super-Earth mass planets around halo stars provides important insights into planet-formation processes in the early days of the Milky Way.

Description: We report the discovery of nine metal-poor stars with high levels of r -process enhancement (+0.81 ≤ [Eu/Fe] ≤ +1.13), including six subgiants and three stars on the red horizontal branch. We also analyse four previously known r -process-enhanced metal-poor red giants. From this sample of 13 stars, we draw the following conclusions. (1) High levels of r -process enhancement are found in a broad range of stellar evolutionary states, reaffirming that this phenomenon is not associated with a chemical peculiarity of red giant atmospheres. (2) Only 1 of 10 stars observed at multiple epochs shows radial-velocity variations, reaffirming that stars with high levels of r -process enhancement are not preferentially found among binaries. (3) Only 2 of the 13 stars are highly enhanced in C and N, indicating that there is no connection between high levels of r -process enhancement and high levels of C and N. (4) The dispersions in [Sr/Ba] and [Sr/Eu] are larger than the dispersions in [Ba/Eu] and [Yb/Eu], suggesting that the elements below the second r -process peak do not always scale with those in the rare Earth domain, even within the class of highly- r -process-enhanced stars. (5) The light-element (12 ≤ Z  ≤ 30) abundances of highly- r -process-enhanced stars are indistinguishable from those with normal levels of r -process material at the limit of our data, 3.5 per cent (0.015 dex) on average. The nucleosynthetic sites responsible for the large r -process enhancements did not produce any detectable light-element abundance signatures distinct from normal core-collapse supernovae.

Description: We have observed 15 red giant stars in the relatively massive, metal-poor globular cluster NGC 4833 using the Magellan Inamori Kyocera Echelle spectrograph at Magellan. We calculate stellar parameters for each star and perform a standard abundance analysis to derive abundances of 43 species of 39 elements, including 20 elements heavier than the iron group. We derive 〈[Fe/H]〉 = –2.25 ± 0.02 from Fe i lines and 〈[Fe/H]〉 = –2.19 ± 0.013 from Fe ii lines. We confirm earlier results that found no internal metallicity spread in NGC 4833, and there are no significant star-to-star abundance dispersions among any elements in the iron group (19 ≤ Z  ≤ 30). We recover the usual abundance variations among the light elements C, N, O, Na, Mg, Al, and possibly Si. The heavy-element distribution reflects enrichment by r -process nucleosynthesis ([Eu/Fe] = +0.36 ± 0.03), as found in many other metal-poor globular clusters. We investigate small star-to-star variations found among the neutron-capture elements, and we conclude that these are probably not real variations. Upper limits on the Th abundance, log (Th/Eu) 〈 –0.47 ± 0.09, indicate that NGC 4833, like other globular clusters where Th has been studied, did not experience a so-called actinide boost.

Description: We have analyzed the double-lined eclipsing binary system ASAS J180057-2333.8 from the All Sky Automated Survey (ASAS) catalogue. We measure absolute physical and orbital parameters for this system based on archival V -band and I -band ASAS photometry, as well as on high-resolution spectroscopic data obtained with ESO 3.6 m/HARPS and CORALIE spectrographs. The physical and orbital parameters of the system were derived with an accuracy of about 0.5–3 per cent. The system is a very rare configuration of two bright well-detached giants of spectral types K1 and K4 and luminosity class II. The radii of the stars are R 1 = 52.12 ± 1.38 and R 2 = 67.63 ± 1.40 R and their masses are M 1 = 4.914 ± 0.021 and M 2 = 4.875 ± 0.021 M . The exquisite accuracy of 0.5 per cent obtained for the masses of the components is one of the best mass determinations for giants. We derived a precise distance to the system of 2.14 ± 0.06 kpc (stat.) ± 0.05 (syst.) which places the star in the Sagittarius–Carina arm. The Galactic rotational velocity of the star is s = 258 ± 26 km s –1 assuming 0 = 238 km s –1 . A comparison with PARSEC isochrones places the system at the early phase of core helium burning with an age of slightly larger than 100 million years. The effect of overshooting on stellar evolutionary tracks was explored using the mesa star code.